Railway traffic controlling apparatus



y fi 1942- L."H. PETER ETAL 2,284,015

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed March 9, 194 5 Sheets-Sheet 1 Fig 4. mRB U I \D-O.

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RAILWAY TRAFFIC CONTROLLING APPARATUS Filed March 9, 1940 5 sheets-Sheet 2 -,9--,kfig 2.

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RAILWAY TRAFFI'c CONTROLLING APPARATUS Filed March 9, 1940 5 Sheets-Sheet 5 fig 6 V ,Ziu/en/Or; la: /6 1 7222? fl g/0: Q W14- M W 2f JT/farneg:

Patented May 26, 1942 RAILWAY TRAFFIC CONTROLLING APPARATUS Leslie Hurst Peter and Douglas Goldie Shipp, King's Cross, London, England,.assignors, by mesne assignmenta'to The Union Switch and Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application March 9, 1940, Serial No. 323,196 7 In Great Britain March 10, 1939 Claims. '..(.o1.246-3) This invention relates to railway trafiic controlling apparatus of the kind in which the selective operation of a number of traffic controlling devices such as railway points and signals is arranged to be electrically effected from a point of control by means of code currents transmitted through line wires connecting the point of control and the devices to be controlled. The latter are usually divided into groups corresponding to local regions of control, termed field stations, and the apparatus enables any desired field station and any desired device at that station to be selectively operated, arrangements being usually provided for indicating at the point of control, also by means of codes transmitted through the line wires, the setting or operation of-the devices at the field stations and other information such as the occupancy of track sections by trains or vehicles.

Centralised traffic control systems of this character are now well known, and the present invention has for its object to provide certain improvements therein which are however not limited to any particular code system.

It is in some cases desirable that agroup of devices normally constituting a field station and arranged for centralised control in the manner above described, should be also arranged for local control from a subordinate point of control located adjacent to the station, it being understood that the centralised and local controls are alternative to one another. The present invention provides arrangements for this purpose whereby the transfer from centralised to local control conditions is effected in a simple, safe and reliable manner. a

According to the principal feature of the invention, the transfer from centralised to local control is eiiected by the transmission of a special control code signal for this purpose from the central point, the reception of this code signal at the field station being arranged to render operative at. the station suitable arrangements which permit local control levers, switches or their equivalent to efiect the operation of one or their normal positions or settings, the establishment of the local control when thus permitted" being actually eiiected'by the local operator set-' ting a king lever or switch which efiects directly or through suitable relays the disconnection of the transmission line, the operating circuits or relays of the devices to be controlled being transferred to the local control levers or switches by the action ofrelays controlled by the special conmore of the track switches, signals, or other traffic controlling devices, at the field station,

these arrangements when thus rendered operatrol code signal above'referred to.

This special code signal maybe arranged to energise a suitable relay atthe field station receiving apparatus, for example, the relay 'IXS or IYS normally provided for signal control in the centralised traffic control system of the Westinghouse Brake 8: Signal CompanysBritish Patent No. 399,539, dated April 4, 1932, which corresponds with the United States application, Serial No. 538,380, filed May 18, 1931, by C. S. Snavely et al. for Remote control systems. It is to be understood that the relay selected for this pur- Figure 1 of the drawings is a diagram of a simple form of field station: to which the invention may be applied. Figures 2 and '3 are diagrams of connections of portions of two of the storage units at the field station adapted for the control of the traflic governing apparatus at the field station in accordance with one form of the invention. Another. form ofthe invention is illustrated in Figures 4, 5, 6 and-"7 of which,

Figure 4 is a view similar to Figure 1 of a field stationcompris'ing shunt signals in addition to main signals. to Figures 2 and 3 of portions of two field storage units at the 'fieldstation and Figure '7 is a diagram of connections of a local control panel cooperating with these storage units, for the control of the shunt signals.

Referring now first to Figures 1, 2 and 3itwill be seen that the field station is located at a portion of the track comprising a main line having track sections DT, ET, FT, and a loop line having .a track section CT and leading to or from the main line through a track switch operated by an electrically actuated point machine W in the usual manner.

Signals RA, RB are provided for controlling traffic from left to right along the main and loop Figures 5 and 6 are views similar lines respectively, together with signals LA, LB for the control of traffic along these lines in the opposite direction.

The relay and other apparatus required for. the code control of the track switch and signals at the field station from a remote point of control are located in a cabin CB which also contains the mal position (for local control) or in its reverse apparatus for local control of the switch and signals. 7 V H The code control apparatus in the cabin -comprises the field station equipment described in the British Patent No. 399,539,.including two field storage unitsFSUl' and FSU2 eachsimilar The portions of the units FSUI and FSUZ with which the present invention is concerned are illustrated in Figures 2 and 3 respectively and the operation of the various relay elements of, these storage units is fully described in the British Pat-, ent No. 399,539.

As therein explained a control code consistin of X, Y and Z code elements is transmitted from the remote point of control to the field station to effect the operation of the relays BXS and 6YS of storage unit FSUI to control the point relay WR controlling the operation of the switch machine W and to also effect the operation of the relays 'IXS; 'IYS of this storageunit to control the signal relays LHS and RHS, These relays SXS, BYS, 'IXS and 'IYS are energized through circuits controlled by delivery relay Dfrom conductors 25, 21, 28, 29 leading from the field coding unit.

An interlocked change-over relay, QR (see Fig ure 3) is provided which is adapted to be set into its normal position or into its reverse position according to whether its energising coil N or its energising coil R is energised. Relay QR may, for example, be of the type shown in Letters Patent of the United -States No. 2,164,823, granted July 4, 1939, to Kershaw etal.

The relay QR when set into its normal position closes a number of contacts .QR(N) interposedin various circuits of the apparatus as shown in Figures 2 and 3, andamongst others the circuits leading from the conduc'tors56, 51 of the storage unit FSUI to the point relay WR and the circuits leading from the wires 58, 59 of the unit FSUI to the signal relays LHS and RHS. Furthermore, when the relay QR. is in its normal position the circuits'of the wires 26, 21, 2'8, 29 leading from the field coding unit to the contacts of the delivery relay Dare also completed through contacts of the relay QR indicated at QR(N) r A point control lever P having contacts P(N), P(R) closed respectively when the lever is in its normal and reverse positions is provided at the field station for effecting local control of the point relay WR, a signal control lever S being similarly provided adapted normally to occupy a central position in'which a contact S(N) is closed and to. be set to a right or left position in which a contact SR(R) or SL(R) is closed to energise the signal relay LHS or RHS so as to clear the signals RA and RB or LA' and LB, it'

position (for central control) when moved there- The king lever K is arranged, when inits reverse position, to lock mechanically or otherwise the local control point and signal levers P, S so "that these cannot be operated. The king lever to the unit illustrated in Figure of this patent. I

K when in its reverse position is also arranged to complete through contacts K(R) the circuits of conductors 28, 29 leading to the delivery relay D ofthe field storage unit FSU2 so as to permit this unit to transmit the special code signal to the appropriate relay 'IYS in this unit.

The operation of the apparatus is as follows:

7 Under central control conditions, the king lever K being in its reverse position the control of the point relay WR is efiected by the relays BYS 'and BXS of the field storage unit FSUI in the manner described in the prior patent since the conductors 56, 51 leading from the contacts of these relays are connected to the point relay WR throughthe closed contacts QR(N) of the change-over relay QR. The relay QR is maintained in its normal setting when the king lever K is in its reverse position in the following manner.

Relay 'IYS of storage unit FSU2 is normally deenergised while relay 'IXS of this unit is normally maintained energised through a local stick circuit from terminal B, conductor 46, front contact B2 of relay 'IXS, contact DI of relay D, back contact 04 of rela 'IYS and the energising coil of this relay to terminal C. An energising cir-- cuit forrelay XQR is completed from terminal B, conductor 55, back contact A5 of relay TYS, front contact A5 of relay 'IXS, conductor 58 a back contact YQR2 of relay YQR, the energising coil of relay XQR to terminal C.

Relay XQR being thus energized a circuit is I completed from terminalB through front contact XQRI of relay XQR and coil QRN of changeover'relay QR, to terminal C. This circuit also includes the contacts of the switch indication relay KR and of the signal relays LH and RH shown in Fig. 11 of the prior patent so as to ensure the usualsafety conditions.

The relay QR being thus set into its normal position the control 'of the point relay WR and the signalrelays LHS and RHS can be effected through the storage unit FSUI by'remote code control in the manner described in the British Patent'No. 399,539 since the circuits of the conductors'involved, 'viz., 56, 51, 58, 59, and 29,28, 21, 26 are all completed at the contacts QR(N) of the relay QR.

Under these conditions the king lever K is held locked in its reverse position owing to the energising circuit of the lock KL being interrupted at thecontact QR(R) ofthe'relay QR.

- When it is desired to establish local control at thefield station, a special code signal is transmitted from the central point to the station and since the contacts K(R) ofthe king lever K are closed, current is transmitted from the field coding unit through conductor 29 and the delivery relay D of storage unit FSU2 to energise relay IYS of this storage unit, relay 'IXS having been deenergised by the interruption of its stick circuit atthe contacts of the delivery relay D. Re-' lay 'IYS having been thus energisedland relay IXS deenergised, a stick circuit for relay TYS is completed through conductor '46 as will be evident from Figure 3. The deenergisation of relay 'IXS will interrupt the circuit of relay XQR at front contact A of relay lXS and (relay IYS being energised) will complete an energising circuit for relay YQR from terminal B, conductor 55, front contact A5 of relay IYS, back contact B4 of relay 'IXS, conductor 59, back contact XQRZ of relay XQR, and coil of relay YQR to terminal C.

Relay XQR being thus deenergised and relay YQR energised a circuit is completed from terminal B contacts of the track switch and signal indication relays above referred to (thereby ensuring that the track switch and signals are in their normal positions), front contact YQRI of relay YQR,-coil R of relay QR to terminal C. The circuit of coil N of relay QR is interrupted at the contact XQR! of relay XQR and the energisingcircuit of the lock KL is completed at contacts YQRH and QR(R). Accordingly when the local operator moves the king lever K from its reverse position towards its normal position so as to close a contact AE (this contact being closed during the intermediate range of movement of lever K from one position to another), the lock KL is operated and the lever K is free to be fully moved to its normal position.

Until however, the lever K is actually moved from its reverse position the operator at the central point can evidently cancel the operations' effected by the special code signal, since the circuits of the conductors 28, ZB'at the storage unit FSUZ are still completed at the contacts K(R) and the storage unit FSUZ is consequently still in communication with the central point ofcontrol.

The setting of the relay QR from its normal position will, however, interrupt the circuits of the conductors 26, 2?, 28, 29 at the contacts QR(N) of field storage unit FSUI, so that control of the points and signals from the central point is no longer possible.

As soon, however, as the local operator has moved the king lever K from its reverse 'posie tion the circuits of the conductor 28, 29 of storage unit FSUZ will be interrupted at the contacts K(R) so that code control from the central point is cut off.

The movement of the king lever K to its nore mal position is arranged to complete a second holding circuit for relay 'EYS of the storage unit FSUZ extending from terminal B over the lever contact K(N) and conductor 41, so that this relay and consequently relay YQR will beheld energised as long as lever K remains in its normal position irrespective of any operation of the delivery relay D. The opening of the contacts QR(N) and the closing of the contacts QRCEt) of the storage unit'FSUl is effective to release the local point and signal levers P and S for operation and by setting the point lever P to its normal or reverse position the relay WR is correspondingly energised through circuits including contacts QR(R) of relay QR and contacts P(N) or P(R) oi lever P and also the contacts of the usual approach locking and track relays LMR, RMR and ETR which as here shown are arranged as shown in Figs. 8 and 9 of the British Patent No. 415,787, dated March 3, 1933, and therefore need not be described in detail.

7 however, still releasable, since relay QR is in its by the signal lever S which effects the energisation or the signal relays LHS or RHS throughcircuits including the contacts SL(R) and SR(R) of lever S, contacts QR(R) of relay QR' and interlocking contacts RHSI and LHSI of the relays RHSandLHS.

It will be noted that the local energising circuits for both the relays LHS and RHS include a front contact GSRI of a stick relay GSR, the relay GSR being energised when the lever S is at normal and maintained energised until a train or vehicle enter track section E and deenerises the corresponding track relay so as to interrupt the stick circuit of relay GSR at track relay contact ETRI As shown in Figure 3, an indication lamp KLL is provided the circuit of which is completed when relay YQR is energised (so as to close front contact YQRI) and contact QR'(R) of relay QR is closed. The lamp KLL will thus indicate to the localoperator when the king lever K is free tobe operated as above described.

The operations of the change-over relay QR and of the king lever K are indicated at the central point of control by the transmission of indication codes each of which includes an impulse having an X, Y or Z characteristic controlled through the conductor 35 of storage unit FSUZ. as follows: As soon as the change-over relay QR has been set to its reverse position so as to release the lock KL of the king lever K, a starting circuit is closed in Fig. 3 from terminal B over contacts K(R) and QR R to conductor 54 which, as shown in Fig. '10 of British Patent No. 399,539, includes a back'contact C3 of a valve relay EV. Theclosing of this circuit initiates the transmission of a code in which the impulse controlled over conductor 35 has a Z characteristic. At the end of this code relay IV picks up to open the circuit over conductor 54 and to prepare an alternative starting circuit over con ductor 48. When the lever K has been moved to its normal position for establishing local control the alternative starting circuit is completed by a connection from terminal B over contacts QR(R) and K(N) to conductor 18. This in itiates a code in which the impulse controlled over conductor 35 has a Y characteristic, whereupon the valve relay "IV is released to openthe circuit including conductor 48 and to' again prepare the one including conductor 54. 1

When it is desired to re-establish central control, the action is initiated by the local operator, who after setting the track'switch and the signals to normal, will move the king lever K to its reverse position, the lock'KL on this lever being,

reverse position. The setting of the king lever K to reverse will complete the 'circuitsof the conductors 2,8, 28 of the storage unit FSU2 at lever contacts K(R) and will again complete the starting circuit which includes conductor 54,'to'

initiate a code to cause a Z code impulse tobe transmitted to the central point of control through lever contact K(R) relay contact QR(R) and conductor 35 of storage unit FSU2.

.The operator at the central point being thus Similarly-the signals may be locally controlled notified that local control is to be'terminated,

will transmit a special code signal to cause the energisation of the relay 'IXS andthe release of relay lYS of the storage unit FSU2 so as to energize relay XQR and release relay YQR; and thereby restore the change-over relay "QR; to normal. The control circuits of the relays WR,

These indication codes are transmitted,

RHS and LHS will thereby be reconnected to the corresponding conductors of the storage unt FSUI. 'The setting of the relay QR to normal will also prevent the release of the lock KL on the king lever K so that the latter is. held locked in its reverse position. In these settings of the king .lever K and relay QR the starting circuitrprepared as the result of the transmission of .the last code, which extends .toterminal B over contacts K(R)' and.QR(N) to conductor 48 is closed to initiate a code in which an X indication code impulse. is transmitted to the central point of control, through conductor 35 of storage unit FSU2, thereby notifying that the transfer to central control has been completed. The apparatus at the field station is provided with arrangements for. efiecting'release' of the approach locking ofthe track switch after an interval of time in the well knownmanner, this being effected bythe action of a relay JR when control from the central point isestablished.

When on the other hand, local control is established, the release of the approach locking is arranged to, be effected by a slow-acting relay JRS controlled by means of r a push-button switch JRB,' the relayJRS controlling the action of the relay JR. 1

. The occupancy of the track circuits ET, FI, and the setting of the track switch and signals by code control from the central point are arranged to be indicated by codes transmitted from the field station in which the character of the indication impulses is governed. by the relay contact mechanism indicated at M in Figure 2, in a manner which willbe evident withtrack switch of Fig. 1, and relays LGP and RGP are indication relays controlled by the signals like the similarly designated relays in British Patent No. 415,787.

Referring now to the modified apparatus the main signals RA, RB and LA, LB controlled by relays LHS and RHS are arranged to be controlled from the central point only whileshunt signals RAS, RBS and LS are arranged to be controlled locally from the field station only, the control of the track switch being effected either from the central point by code control or by the operator at the field station.

As shown in Figure '7, the. local control apparatus at the field station comprises a control panel T on which are mounted a king switch KS, a point control switch TP and a shunt signal control switch TS. Two additional relays ZR( N) and ZR(R) are also provided at the field station for effecting the same interlocking and code lock-out features as the king lever K in the system previously described.

The relay ZR(N) is arranged to be energised when the king switch KS is in its normal position (for local control) through a circuit from terminal B, back contact ZR(R)| of relay ZR(R) and the coil of relay ZR(N) to terminal C. The relay ZR(R) is 'deenergized under these conditions since its circuit is interrupted at back contact ZR(N) I of relay ZR(N) 7 Relay ZR(R) being deenergized, the circuits of conductors 28, 29 at storage unit FSU2 of Fig-- ure 6 are interrupted at contacts ZR(R)2 and] ZR(R)3 of this relay.

Relay YQR having been energized by central control and change-over relay QR having been thereby set to its reverse position as previously described with reference to the preceding figures, the point relay WR is connected to the contacts of the point control switch TP through conductors TPI and TPZ and as will be apparent from Figures 5 and 7, under these conditions the point relay WR can be energized in the normal or reverse direction by correspondingly actuating the control device TP, through a circuit including the contacts QR(R) of relay QR, the conductors 'IPl, TP2, contacts ZR(N)2 and ZR(N)3 of relay ZR(N).

Similarly, by actuating the signal control device TS, operating current for the shunt signals RAS, RBS or LS is supplied thereto through a circuit including contact ZR(N) 4 of relay ZR(N),

the appropriate contacts of the control device TS,

.minal C. The circuits of conductors 28, 29 of shown in Figures 4, 5, s and '1, it will be seen that r contacts KSN of switch KS,.

storage unit FSU2 of Figure 6 are thereby completed at contacts ZR(R)3 and ZR(R)2 so that the central control of the relays XQR and YQR is again established. Contact ZR(R) 6 completes a starting circuit over conductor 54, causing an indication code to be transmitted which includes a Z impulse controlled over conductor 35. The central oflice operator. then sends a special code signal as hereinbefore described to effect the energisation of relay XQR and the release of relay YQR to thereby restore relay QR to nor mal. When relay QR assumesits normal posi-' tion, the central control of the relays LHS and RHS is again established, central control of the point relay WR being i also restored since the contacts QR(N) of relay QR are closed.

In other respects the operation of the systems is similar to that of the system previously described. 1 r

The local control panel T is provided with an indication lamp TL which is supplied with current when the contacts QR(R) of relay QR are closed so as to indicate that the panel is free for operation. Indication lamps TPN and TPR are also provided on the panel T and are controlled through the contacts of the indication relay KR.

for the track switch so as to indicate the setting of this switch under local control conditions.

It will be understood that the panel T may be provided with control devices similar to the device TS for the control of the signal relays RHS and LHS in addition to or as an alternative to the control device TS for the shunt signals.

It will be understood that in both systems the local control is entirely suspended so long as central control is in operation and can only be permitted to be established by action initiated from the central point and completed by the cooperation .of the local operator. Furthermore, when local control has been established by the local operator, the central control is suspended and can only be restored by action initiated by the local operator and completed by the cooperation of the operator at the central point.

The invention is evidently not limited to the particular arrangements above described and illustrated by way of example which may be modified in various respects without exceeding the scope of the invention.

Having now described our invention, what we claim is:

1. In a railway trafiic controlling system, impulse signaling apparatus for communicating between a central point of control and'a field station, a plurality of railway trafiic governing devices at said station, and a dual system of control for said devices comprising control relays responsive to impulse signals transmitted at times 7 from the central point of control for controlling the operation of said devices, manually operable control levers at another point of control for at other times controlling such operation by the operation of said levers, and change-over means responsive to a special impulse signal transmitted from the central point of control for effecting the transfer from central control to the control of said devices by said levers.

2. In a railway traffic controlling system, impulse signaling apparatus for communicating between a, central point of control and a field station, a plurality of railway traific governing devices at said station, control relays responsive to impulse signals transmitted at times from the central point of control for controlling. the operation of said devices, manually operable control levers at a local 'point of control for at other times controlling such operation .by the operation of said levers, and change-over means responsive to a special impulse signal trans- .mitted from the central point of control .pro-

vided all of said devices are in their normal condition for effecting. the transfer from central control to the local control or from local control station, a plurality of railway traific governing devices at said station, a, change-over relay and a king lever at said station each having a normal and a reverse position, "a plurality of control relays at said station responsive to impulse signals transmitted from said central point and effective only when said change-over relay is in its. normal position to control said devices, a plurality of control levers at said station for controlling said devices locally, said levers being eflective only when said change-over relay is in its reversed position, other control relays at said station responsive to special impulse signals transmitted from said central point for operating said change-over relay from normal to reverse or from reverse to normal when-said king lever is reversed, and circuit means efiective as long as said king lever is normal to prevent the operation of said change-over lever in response to said special impulse signals.

4. Ina railway trafiic controlling system, impulse signaling apparatus for communicating .between a central point of control and a field station, a plurality of railway trafiic governing devices and a change-over relay at said station, a plurality of control levers at said station for controlling said devices locally said devices being subject to control in accordance with the positions of said levers only when said changeover relay is in a reversed position, means for controlling said devices in accordance with the character of difierent impulse signalstransmitted from said central point efiective only when said change-over relay is in a normal position, and means for controlling said change-over relay in accordance with the character of special impulse signals transmitted from said central point.

5. In a railway trafiic controlling system, impulse signaling apparatus for communicating between a central point of control and a field station, a plurality of railway traffic governing Y devices and a change-over relay at said station,

a plurality of control levers at said station for controlling said devices locally said devices being subject to control in accordance with the positions of said levers only when said changeover relay is in a reversed position, means for controlling said devices in accordance with the character of 'difierent impulse signals transmitted from said central point effective only when said change-over relay is in a normal position, a locally operable king lever at said station, and means eifective only when said king lever is in its reversed position for controlling said change-over relay in accordance with the character of special impulse signals transmitted from said central point, and an indication lamp associated with said king lever for indicating theposition of said change-over relay.

6. In a railway trafiic controlling system, impulse signaling apparatus for communicating between a central ,point of control and a field station, a plurality of railway trafiic governing devices and a change-over relay at said station, a'plurality of control levers at said station for controlling said devices locally said devices being subject to control in accordance with the positions of said levers only when said change-over relayis in a reversed position, means for controlling said devices in accordance with the character of difierent impulse signals transmitted from said central point efiective only when said change-over relay is in a normal position,

a locally operable king lever at said station,

means effective only when said king lever is reversed for controlling said change-over relay .in accordance with the character of special impulse signals transmitted from said central point, locking means for preventing operation of said king lever, and means effective only when said change-over relay is reversed for energizing station, a plurality of railway trafiic governing devices and a change-over relay atsaid station, a plurality of control levers at said station for controlling said devices locally said devices being subject to control in accordance with the positions of said levers only whensaid changeover relay is in a reversed position; means for controlling said devices in accordance with. the character of difierent impulse signals transmitted from said centralpoint effective only when said change-over relay is in a normal position, a locally operable king lever at said astation, means efiective only When said king lever is in its reversed position for operating said'changeover relay from normal to-reverse in response to a special impulse signal transmitted from said central point, means for transmitting a distinctive impulse signal to said central point when the change-over relay assumes its-reversed position, means for transmitting'a different impulse signal to said central point in response to the subsequent operation of said king lever to its normal position, and means for locking said change-over relay in'its reversed position when said king lever is in its normal position.

8. In a railway traffic controlling system, im-

pulse signaling apparatus for communicating between a central point of control and a field station, a plurality of railway trafl'ic governing devices and a change-over relay at said station, a plurality of control levers at said station for controlling said devices locally said devices being subject to control in accordance with the positions of said levers onlywhen said change-over ,relay is in a reversed'position, means for controlling said devices in accordance with the character of different impulse signals transmitted from said central point effective only when said change-over'rela'y is in a normal position, .a locally operable king lever at said station, means effective only when said king'lever'is in its rever's'e'd position for operating said change-over 'relay to reverse "or to normal in response to special signals transmitted from said central point, means for transmitting distinctive impulse signals to said central pointto indicate the position assumed by said change-over relay, means for locking said king lever in its reversed position when said change-over relay is in its nor- ,mal position, and means adjacent said king lever controlled by said change-over relay to indicate when saidlocking is released. s

9. In a railway traflic controlling system, im-

vices' and a change-over relay at saidstation, a

plurality of control levers at said station for controlling said devices locally said devices being "subject to control in accordance with thepositions of said levers only when said change'fover relay is in a reversed position, means for controlling said devices in accordance with the character of different impulse: signals transmitted from said central point effective only when said change-over relay is in a normal position, a locally operable king lever atsaid station, means for transmitting a distinctive impulse signal to said central point in response to the operation said change-over lever is in its reversed position, means effective only when said king lever its reversed position for operating said including said communication system for con trolling said switch and signals from said central point, switch andsignal levers at said station for locally controlling said switch and signals, change over relay means at said station which in one position renders said switch and signals subject to control from said central point and in another pulse signaling apparatus for communicating .be- .tween a central point of control and a field station, a plurality of railway traflic governing deof said king lever from normal to reverse when position 'renders said switch and signals subject to control'by said levers, 'aridmeans including said; communication system for controlling the position of said change-over relay means .from said central point. I. v 11. In a centralized traflic control system. for railroads,- a communication system connecting a central point of control and a field station, a track switch at said station,: signals forigove erning trafiic movementslover saidswitch,ia;dual system of control for said switch and signals'com, prising means including said communication system for controlling the operation: of said I'SWj-tCh and signals from said central point, switch and signal levers for controlling .such'Qoperation of said switch and signalsfrom a second:point.oi control, change-over relay means Lwhichiin one position renders saidswitch and-signals subject to'c'ontrol from saidcentral point andiin another position renders said switch'andsignals subject to control by said levers,mean's including said communication system for, controlling the :position of said change-over relay means from said central point, and'means controllable locally at said second point of control fo'r at 1 times 'pre': venting a change inthe positionlof said pchangeioverrelaymeans. r1 'i 12. In a centralized traffic control system for railroads, a communication system'connecting a central point of control and a field station, a track switch at said station, signals for gov.-

erning traflic movements .over said switch, means including said communication system for con- .trollingthe operation of said switchand signals from said central point, switch and signal levers for locally controlling 'suchcoperation or said switch and signals, change-over. relay. means which in one position renders said switch and signals subjectto control 'from said central point and in another position renders said switch and signals subject to control by 'said levers, means including said communication'system for controlling the positionof' said change-over relay means from said central "point, and means for preventing a change in the position: of said change-over relay means except when said switch and signals are in their normal positions.

13. In a centralized traflic control system for railroads, a code type communication system connecting a. central point of control and a field station, a track section at said station, main signals and shunting signals for governing traflic movements over said section, code responsive'relays controlledthrough the medium of said coinmunication system for controlling the operation of said mainsignals from said central point, a signal lever for locally controlling the operation of said shunting signals, change-over relay means which in one position renders the. operation of said main signals subject to control by said code responsive relays and in another position renders the operation of said shunting signalssubject to "control by said lever, and other code responsive relays controlled" through the medium ofsaid communication system for controlling the position ofsaid change-over'relaymeans from said central point. 7

14. In a centralized traflic control system iorrailroads, a communication 'systmconnecting a central point of controlland a fieldstatioma track switch at said station} means including said communication system forcontrolling the" operation of said track switchfrom the central point, 'a switch lever for' controlling such 'o'peration'of 'thetrack s'witch, change-over relay meanswhich one position rendejrssaid switch'siibject control'fromsaid central point and'in another positrack switch, change-over relay means which in one position renders said switch subject to control from said central point and in another position renders said switch subject to control in ac-- cordance with the position of said switch lever, and means efiective only when the track switch and its control lever are both in their normal positions for controlling the position of said changeover relay means from said central point.

LESLIE HURST PETER. DOUGLAS GOLDIE SHIPP. 

